Method for performing a partial atherectomy

ABSTRACT

A catheter atherotome and method for its use for performing partial atherectomy in an artery and blood flow through the artery. Several blades are mounted at a distal end of a catheter, in a helical basket configuration and spaced angularly apart from one another about the associated ends of two concentric sheaths in such a way that longitudinal and rotary relative movement of the sheaths selectively bows the blades arcuately outwardly into a cutting position or draws the blades flat into alignment with the sheaths. The blades have sharpened cutting edges extending helically and directed toward the cathether&#39;s proximal end when the blades are bowed. Partial removal of an atheroma is effected by manually pulling the basket knife past an atheroma with the basket blades in their outwardly bowed cutting positions, with the speed, force, and amount of expansion of the blades determined by the operator. Removal of cut-away pieces of atherosclerotic plaque material is accomplished either by pull-back of a balloon embolectomy catheter or by use of a latex membrane enshrouding the spiral wire blades to trap the shavings within the membrane.

This application is a continuation of my co-pending U.S. patentapplication Ser. No. 07/616,240, filed Nov. 20, 1990, now abandoned,which is a division of U.S. patent application Ser. No. 395,500, filedAug. 18, 1989, now abandoned.

BACKGROUND OF THE INVENTION

The present invention relates to surgical apparatus and procedures, andparticularly to a device for excising portions of the atheroscleroticplaque material causing stenosis in an artery.

Atherosclerosis (Greek for soft and hard deposits) is a condition whichprogressively affects many arteries of the body with advancing age. Itultimately produces thicknening of the medial layer of the arterialwall, which may involve some or all of the circumference of the bloodvessel. Eventually, narrowed internal diameter, or stenosis, of theartery results and restricts the flow of blood to the tissue beyond thestenosis, producing symptoms incuding angina or myocardial infarction inthe heart, claudication or gangrene in the legs, high blood pressure, ordeterioration of kidney function.

The art and science involved in modern vascular surgery arecomparatively young and began with the successful end-to-end repair ofsevered arteries in Korean war casualties. Atherosclerotic narrowing ofarteries then could only be corrected by complete endarterectomy, whichrequired a longitudinal incision through the entire narrowed segment ofan artery. Exposure of an artery for this purpose was difficult, and thewounds resulting from the surgery were large. Although results wereoften gratifying, the practice was not widespread because of resultingproblems such as pseudoaneurysms developing in endarterized segments andthe potential for vessel wall dissection at the distal endpoint, andbecause of the difficulty posed both for the patient and for thesurgeon. During the 1950's a variety of synthetic tubular grafts wereintroduced and perfected for partial arterial replacement and bypassesaround stenoses. Because of the relative ease of such procedures bycomparison with endarterectomy, bypass grafting soon became the dominantmeans of correcting arterial narrowing within the pelvis and thigh.Advances in surgical technique in the late 1960's made possible the useof the patient's own reversed saphenous vein to bypass occluded arterieson the heart and below the knee.

As the population of the United States has aged as a group, themanifestations of atherosclerosis have, as a group, become this nation'snumber one health problem in terms of both suffering and cost. Whilesurgical bypass procedures using saphenous vein or prosthetic conduitremain the procedure of choice in most instance, newer technologies haveevolved in the last decade to simplify the treatment of atheroscleroticstenoses in an attempt to reduce patient risk, reduce cost, and to maketreatment available to more people. In carefully selected casesinvolving narrowing of short segments of the coronary, renal, iliac, andfemoral arteries balloon dilation has been employed with some success.Generally, however, the duration of arterial patency resulting from suchprocedures is less than for bypass graft procedures. Utilization oflasers to open narrowed arteries has not yet proven to be clinicallysuccessful and is very expensive in all aspects.

In recent years a variety of atherectomy devices have been usedexperimentally in attempts to extend patency. Some of these devicesinclude rotary cutting mechanisms, which restrict their use to stenosesof short length. Some are driven by high-speed electric motors which addto their complexity and increase the likelihood of breakdown while alsoreducing the amount of responsiveness and taking the ability to controloperation out of the surgeon's hands.

Manually-operated devices for relieving arterial stenoses are disclosed,for example, in Lary U.S. Pat. No. 4,273,128, which discloses a devicehaving a plurality of curved knife blades whose edges are directedradially outward, and Fischell et al. U.S. Pat. No. 4,765,332, whichdiscloses a catheter including a proximally-exposed annular cutting edgewhich is no greater in diameter than an outer sleeve of the catheter towhich it is attached. Luther U.S. Pat. No. 4,650,466, discloses acatheter which includes an expansible woven tube portion which can beused to abrade atherosclerotic plaque from the interior wall of theartery. Clark, III, U.S. Pat. No. 4,020,847, discloses a catheter deviceincluding a slot having sharp edges extending longitudinally of thecatheter to cut free dangling matter which might otherwise obstruct thelumen of an artery. Hoffman U.S. Pat. Nos. 2,730,101 and 2,816,552disclose teat bistoury devices including blades which can be bowedoutwardly along the length of each blade to protrude radially. Thedevice is intended to be rotated to cut away restrictions in a milkcanal of a cow's teat. Several prior art devices useful for manuallyopening venosus vales are disclosed in Chin et al. U.S. Pat. Nos.4,739,760 and 4,768,508 and Reed U.S. Pat. No. 4,655,217.

Chin U.S. Pat. No. 4,559,927 discloses an endarterectomy apparatusincluding a center-pull annular cutter for removing arterioscleroticmaterial.

Rotary, mechanically operated devices are disclosed in such patents asSokolik U.S. Pat. No. 3,320,957, which discloses a device including anarray of helical stationary blades inside which an oppositely-twistedhelical rotor operates to shear material protruding inwardly between thestationary blades. Auth U.S. Pat. No. 4,445,509 discloses a flutedrotary burr. Kensey U.S. Pat. Nos. 4,589,412 and 4,631,052 discloseturbine-driven rotary devices for opening obstructed arteries, andKensey et al. U.S. Pat.No. 4,681,106 discloses another turbine-drivenrotary cutting device.

Several devices for use in retrieving stones from within bodilypassageways by entrapping the stones within baskets including arrays ofhelical wires are disclosed in Grayhack et al. U.S. Pat. No. 4,611,594,Duthoy U.S. Pat. No. 4,625,726, Dormia U.S. Pat. Nos. 4,347,846 and4,612,931. Related devices are disclosed by McGirr U.S. Pat. No.4,807,626, and Hawkins, Jr. et al. U.S. Pat. No. 4,790,812, whichdiscloses a parachute-like basket carried on a distal end of a rotatableinterior member of a catheter so that the parachute-like basket canretrieve particles cut free by the interior member of the catheter. ParkU.S. Pat. No. 3,704,711 discloses a device in which a radially outwardlydisposed edge can be controllably concealed within a distal end of acatheter or exposed so that the blade can be used.

Balloon-tipped catheters are disclosed in Fogarty U.S. Pat. No.3,435,826, while Fogarty U.S. Pat. No. 3,472,230 discloses a catheterincluding an umbrella-like skirt useful for retrieval of stones.

There still remains a need, however, for an improved atherectomy devicewhich is simple in concept and operation, manually operable, andimmediately responsive, and which is useful for all stenoses regardlessof the length of the area of stenosis.

SUMMARY OF THE INVENTION

The present invention overcomes some of the shortcomings anddisadvantages of the devices disclosed in the prior art by providing acatheter atherotome which is manually operable and by which a surgeoncan plane away atherosclerotic plaque from within an artery by enteringthe artery with a catheter at a single point proximal to the plaquedeposit. The plaque is cut away piecemeal, by serial pullback strokes ofa basket knife carried on the distal end of the catheter and which iscollapsible to a small diameter conforming to the diameter of thecatheter itself. The basket knife of the catheter atherotome includesseveral blades which are aligned generally parallel with one another andin a generally helical arrangement about an inner portion of thecatheter which extends distally beyond the distal end of an outer sheathportion of the catheter when in a retreated, relaxed configuration.Respective ends of each blade are attached to the inner member and theouter sheath of the catheter so that when the distal end of the innermember is moved closer to the distal end of the outer sheath the blademembers are forced to bow outward, expanding the basket knife radially.When the blades are bowed outward, sharpened edges of the blades areexposed proximally with respect to the catheter, so that moving thecatheter proximally brings the edges to bear against atheroscleroticplaque deposits to cut them away from the interior of an artery.

while it is particularly well-adapted for use in the femoral andpopliteal arteries, the catheter atherotome of the invention may be alsouseful in the tibial and peroneal, arteries, and with entry gained viathe aorta, in the heart and renal arteries.

In a preferred embodiment of the invention, both the longitudinalposition and the rotational position of the inner member of the catheterare adjustable relative to the outer sheath, and the several blades areflexible, so that both the pitch and the amount of radial bowing of theblades are controllable. Preferably, the angle of attack of thesharpened edge is such that it will engage atherosclerotic plaque butnot normal arterial lining tissue.

Another embodiment of the invention utilizes a more rigid basket knifein which sharpened portions of the blades overlap one another to providecomplete circumferential coverage of the interior of an artery.

Yet another embodiment of the basket knife portion of the deviceincludes cutting edges over only about half of the basket circumference,so that aterectomy can be performed on one-half of the arterial wall inlocations where atherosclerosis normally involves only the posteriorone-half of the artery.

Preferably, a lumen is provided in the inner member of the catheter, anda balloon-tipped catheter such as a Fogarty® catheter is utilized tocollect shavings of plaque cut free by the catheter atherotome of theinvention, so that the shavings can be surgically removed through anincision in the arterial wall after atherectomy has been performed.

In another embodiment of the invention a latex skirt is provided tosurround the basket knife assembly except where the cutting edges areprovided, so that the shavings are trapped within the basket during eachcutting pass of the basket over the plaque. This embodiment is intendedfor use in smaller arteries where it might be awkward or impractical toinsert balloon-tipped catheter, or where the catheter atherotome isintroduced into an artery percutaneously.

In percutaneous use of the catheter atherotome of the invention a needleis inserted through the skin into an artery. A guide wire is passedthrough the needle bore and directed to the point of stenosis in thearterial system. The needle is removed and a dilator is passed over theguide wire and then removed, after which the catheter atherotome isinserted into the artery following the guide wire through the dilatedtract into the artery and on to the point of stenosis. After appropriateexcision of atherosclerotic plaque, the catheter atherotome and guidewire are removed and pressure is held at the point of skin puncture topermit closure of the artery to occur.

Objective confirmation of enlargement of the arterial lumen by the useof the catheter atherotome could be obtained either by on-the-tableangiography, for comparison with the pre-operative arteriogram, or anon-the-table duplex-ultrasound measurement could be made of the arteriallumen immediately before and after use of the catheter atherotome of thepresent invention.

It is, therefore an important object of the present invention to providean improved catheter atherotome for use in relief of stenoses inarteries.

It is another important object of the present invention to provide sucha device which is manually adjustable between a configuration in whichcutting blades are retracted and a configuration in which cutting bladesare operatively positioned and exposed to a degree controllable by theuser of the device.

It is an important feature of the apparatus of one embodiment of thepresent invention that its blades are somewhat flexible, between aposition in which they move along the interior of healthy portions of anartery, and a position in which they cut away atherosclerotic plaque.

The foregoing and other objectives, features, and advantages of theinvention will be more readily understood upon consideration of thefollowing detailed description of the invention, taken in conjunctionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a pictorial view of a catheter atherotome which embodies thepresent invention, with the catheter portion shown foreshortened, andwith the basket knife in a retracted or closed position.

FIG. 2 is a sectional view of the catheter atherotome shown in FIG. 1,taken along the line 2--2 of FIG. 1, and simplified by omission of someof the blades of the basket knife.

FIG. 3 is a view similar to FIG. 2, with the basket knife in anexpanded, or cutting configuration.

FIG. 4 is an edge-on view of one of the blades of the basket knife ofthe atherotome shown in FIGS. 1-3.

FIG. 5 is a side view of the blade shown in FIG. 4.

FIG. 6 is a sectional view, taken along line 6--6 of the blade shown inFIGS. 4 and 5.

FIG. 7a is a perspective view, taken in the direction indicatedgenerally by line 7a--7a of FIG. 1, showing a fitting for attaching thedistal end of each blade to the end of the inner member of the catheteratherotome shown in FIGS. 1-3.

FIG. 7b is a perspective view, taken in the direction indicatedgenerally by the line 7b--7b in FIG. 1, of the fitting attaching theproximal ends of the blades to the distal end of the outer sheathportion of the catheter atherotome shown in FIGS. 1-3.

FIG. 8 is a schematic view showing the arrangement of several blades ofone embodiment of the catheter atherotome of the present invention.

FIG. 9 is a view similar to that of FIG. 8, of a set of somewhatdifferent blades for the basket knife of the catheter atherotome ofFIGS. 1-3.

FIG. 10 is a view similar to that of FIG. 8, schematically showing athird set of blades which embody the invention.

FIG. 11a is a pictorial view of the basket knife portion of a catheteratherotome of an alternate embodiment of the invention, including askirt portion associated with the blades of the basket knife.

FIG. 11b is a fragmentary side elevation view showing a detail of theembodiment o the invention shown in FIG. 11.

FIGS 12a, 12b, and 12c are sectional views of a portion of an arteryincluding an atheroma, showing the action of the catheter atherotome ofthe present invention as it is drawn past the atheroma to remove aportion of the plaque material forming the atheroma.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings which form a part of the disclosureherein, in FIGS. 1-3 a catheter atherotome 10 includes an elongateflexible tubular outer sheath 12. A similar inner member 14 of somewhatgreater length is disposed within the of the outer sheath 12. The outersheath 12 and inner member 14 are flexible enough to negotiate curves inarteries a traumatically but are rigid enough to maintain relativeposition between the two, both longitudinally and rotationally. Theymight be made, for example, of a suitable polyvinyl chloride plasticmaterial. Markings 15 may be provided along the outer sheath 12 toindicate the length of the catheter atherotome distal of each marking asan aid to placement in an artery.

A first lever 16 is connected with the outer sheath 12 near its proximalend. A second lever 18 is pivotally connected with the first lever 16 ata pivot joint 19. An elongate loop 20 is attached to the second lever 18and surrounds the rear of proximal end portion 21 of the inner member14. A stop 22 is fixedly attached to the proximal end of the innermember 14. The stop 22 is preferably larger than the loop 20 and isprovided with appropriate surface configuration to permit rotation ofthe inner member 14 manually with respect to the outer sheath 12 by useof the stop 22. Finger loops are provided on the levers 16 and 18 foruse in manipulation of the first and second levers 16 and 18 to withdrawthe proximal end 21 of the inner member 14 a distance from the proximalend 23 of the outer sheath 12, as desired. A second stop 25 ispreferably also located on the inner member 14, on the distal side ofthe loop 20, to be used, if necessary, to push the inner member 14distally into the proximal end 23 of the outer sheath 12. Preferably, ascale 24 is provided on the first lever 16 as an indicator of theposition to which the inner member 14 has been withdrawn relative to theouter sheath 12. A cap 26 is mounted on the proximal, or rear end of theouter sheath 12 by means of mating threads, and an O-ring 28, held inplace by the cap 26, grips the exterior surface of the inner member 14with an appropriately adjustable amount of force to maintain theposition of the inner member 14 relative to the outer sheath 12.

The inner member 14 is tubular, with a lumen which is large enough toadmit passage of a guide wire (not shown) or a balloon-tipped catheter30 which may, for example, be a Fogarty® arterial embolectomy catheter.

A controllably expansible basket knife 32 includes a plurality of blades34 extending between the distal end 35 of the outer sheath 12 and thedistal end 37 of the inner member 14, which extends as previouslymentioned, beyond the distal end of the outer sheath 12. While sixblades, equally spaced, are shown, fewer or more might also be utilized.The catheter atherotome 10 can be of an appropriate size, depending onthe size of the artery, and larger blades 34 are required for largerarteries.

As shown in FIGS. 1 and 2, when the inner member 14 is located with itsdistal end 37 in a position of maximum extension beyond the distal end35 of the outer sheath 12, the blades 34 extend closely alongside theprotruding portion of the inner member 14, normally in a helicalconfiguration centered about a central longitudinal axis 36. The distalends 38 of the several blades 34 are separated from the positions of theproximal ends 40 of the blades 34, by an angle determined by therotational position of the inner member 14 with respect to the outersheath 12. Thus, rotation of the inner member 14 within the outer sheath12 causes a steeper or shallower slope or pitch of each of the blades34. Thus, as shown in FIG. 1, the distal ends 38 of the blades arelocated approximately 60° offset from the respective proximal ends 40,with the blades 34 extending generally longitudinally and closelyalongside the inner member 14, in a steep helix.

It should be recognized that FIGS. 2 and 3, for the sake of clarity,show but two of the blades 34, of which there would normally be agreater number, for example, six blades 34. It should further berecognized that the inner member 14 is shown in a position of rotationrelative to the position of the outer sheath 12 in which the distal ends38 are separated from the respective proximal ends 40 by about 180° .This exaggerates the degree of rotation which probably would be used inpractice, in order to provide greater clarity in the figures fordepiction of the effects of a combination of rotation and retraction ofthe inner member 14 with respect to the position of the outer sheath 12.

Referring now also to FIGS. 4, 5, and 6, it will be seen that each blade34 includes a middle portion 42 including a sharpened edge 44, anintermediate, or strut, section 46, between the distal end 38 and themiddle portion 42, and an intermediate, or strut, portion 48, locatedbetween the middle portion 42 and the proximal end 40. A pair of fins, afin 50 proximate the distal end 38 and a parallel fin 52 proximate theproximal end 40 of the blade, respectively define bores 54 and 56. Thefins 50 and 52 are oriented generally perpendicular to the orientationof a plane defined by the middle portion 42 of the blade, and the bores54 and 56 extend generally normal to the fins 50 and 52, while theblades 34 are gently curved in an "S" shape when relaxed.

The catheter 30 extending through the catheter atherotome 10 has aballoon tip 60 which extends beyond the distant end of the catheteratherotome 10, as may be seen in FIG. 1. The catheter 30 is longer thanthe entire catheter atherotome 10, so that it can be manipulated at theproximal end of the catheter atherotome 10 while extending through alumen 62 defined within the inner member 14, as shown in FIGS. 2 and 3.Such length is also desirable to provide room for cutting strokes of theatherotome with the balloon tipped catheter stationary in an artery.

The intermediate, or strut, portions 46 and 48 of each blade 34 areflexible in response to movement of the inner member 14 relative to theouter sheath 12, so that rotation of the inner member and retraction ofthe distal end 37 of the inner member with respect to the distal end 35of the outer sheath result in flexure of the blades 34. Flexure takesplace particularly in the strut portions 48 and 46 of the blades 34, toexpand the plurality of blades 34 into a basket-like configuration inwhich each edge 44 is inclined more steeply with respect to the centrallongitudinal axis 36. While the strut portions 48 and 46 are free tobend relatively uniformly and to twist, the wider and more flattenedshape of the sharpened middle portion 42 constrains its flexure to adegree which permits the edge 44 to assume an arcuate curvature centeredabout the inner member 14 but at a radius greater than that of the outersheath 12, with the sharpened edge 44 directed toward the proximal endof the catheter atherotome 10. The inclination of the individual blades34, and particularly the edge 44 thereof, is determined by both thedegree to which the inner member 14 is withdrawn proximally within thedistal end 35 of the outer sheath 12, and the degree of rotation of theinner member 14 with respect to the outer sheath 12. Preferably, theedge 44 can extend up to an angle of 40° to 50° relative to an imaginaryequator of the basket knife 32 to achieve maximum cutting, with theequator considered to be normal to the longitudinal axis 36.

As may be seen with reference more particularly to FIGS. 7a and 7b, aswell as FIGS. 2 and 3, the blades 34 are prevented from rotating withrespect to the inner member 14 and outer sheath 12 by the manner inwhich they are attached. An articulating mounting ring 64 extendsthrough the bores 54 of all of the several blades 34. The articulatingmounting ring 64 is securely attached to a distal fitting 66, which hasan ogival shape. The fitting 66 is attached to the distal end 37 of theinner member 14 by exterior threads defined on the inner member 14 andinterior threads in the distal fitting 66. A bore 68 in the distalfitting 66 is an extension of the lumen 62 of the inner member 14.

The articulating mounting ring 64 is attached to the proximal end of thedistal fitting 66 by a plurality of tethering hasps 70 disposed aboutthe proximal end of the distal fitting 66 and equal in number to thenumber of blades 34 to be attached to the distal fitting 66. Each of thetethering hasps 70 is bent inwardly to form an arch over thearticulating mounting ring. Adjacent ones of the several tethering hasps70 cooperatively define radially extending slots 72 between one another,with the fin 50 of a respective one of the blades 34 being disposedwithin each of the slots 72. The slots 72 and fins 50 restrain each ofthe blades 34 from rotation about an axis parallel with the centrallongitudinal axis 36, but permit a terminal portion of each blade,including the fin 50 and the strut or intermediate portion 46, to pivot,about the articulating mounting ring 64 as the blade 34 is bowed.

A proximal fitting 76 is attached to the distal end 35 of the outersheath 12 by exterior threads mated with interior threads defined in theouter sheath 12. An articulating mounting ring 8, similar to thearticulating mounting ring 64, extends through the several bores 56defined by the fins 52 of the blades 34, interconnecting all of theproximal ends 40 of the blades. The articulating mounting ring 78 isattached to the proximal fitting 76 by a plurality of tethering hasps 80equal in number to the number of blades 34.

Similar to the tethering hasps 70, the tethering hasps 80 extend fromthe distal face of the proximal fitting 76 and are bent arcuately inwardtoward the central longitudinal axis 36 of the catheter atherotome 10,arching over and retaining the articulating mounting ring 78. Thetethering hasps 80 define radially extending slots 82 between adjacentones of the hasps 80 and restrict the proximal ends 40 of the severalblades 34 from rotating about an axis parallel with the centrallongitudinal axis 36 of the catheter atherotome 10. Terminal portions ofthe blades 34 located adjacent the proximal ends 40 are free to pivotwith the fins 52 rotating about the articulating mounting ring 78 inresponse to retraction of the distal end of the inner member 14 into thedistal end of the outer sheath 12 to the position shown, for example, inFIG. 3.

Referring to FIGS. 8, 9, and 10, the configuration and degree offlexibility of a set of blades 34 may be made to provide differentamounts of coverage of the circumference of the interior or lumen of anartery within which partial arterotomy is to be performed.

In FIG. 8, six blades 34a for use as part of the catheter atherotome 10according to the present invention are shown in a simplified schematicform as if the articulating mounting rings 64 and 78 had beenstraightened and unwrapped from around the circumference of the innermember 14, while maintaining the circumferential spacing of the blades34a so as to show the angular relationships between their respectiveopposite ends. It will be seen, then, that the angular distance of thedistal ends 38a from the proximal ends 40a is greater than 60° . Thus,the distal end of one of the blades 34a is offset angularly beyond theproximal end 40 of the adjacent blade 34a, and the middle portions 42aof adjacent blades 34a also overlap one another so that the edges 44acooperatively present a substantially continuous circular combination ofcutting edges 44a to remove a layer of plaque from the entire interiorsurface of the atheroma being reduced on each cutting stroke of theatherotome. The blades 34a preferably are stiff enough so that the angleof incidence of the cutting edge is fairly stable, so that the cuttingedge can pare off a thin slice of atherosclerotic plaque or similarmaterial from the interior of an artery during use of the catheteratherotome 10 equipped with the blades 34a.

Referring now more particularly to FIG. 9, a set of blades 34b are shownwhich have less offset between the locations of their distal ends 38band their proximal ends 40b, so that the cutting edges 44b make separatecuts which do not overlap one another ordinarily. However, the blades34b are made with greater flexibility and less torsional rigidity thanthe blades 34a. This is so that, although the angle of incidence of theedges 44 ordinarily is too little to result in cutting the interior ofthe arterial wall, when the sharp edge 44b of an individual blade 34b"snags" on a hard irregular body of plaque the blade is everted into acutting position with a somewhat greater angle of incidence in order toexcise that piece of plaque, as will be explained more fullysubsequently. Because of the lesser offset between the distal andproximal ends of the blades 34b there is an interrupted coverage of thecircumference of an artery, providing space for irregular protrusions ofplaque to project between the blades 34b to be engaged by the sharpenededges 44b.

In FIG. 10 is shown a set of blades 34c and 34d, of which only the threeblades 34c include middle portions 42c having edges 44c, while theblades 34d have no sharpened edge portions. Thus, the set of blades 34cand 34d provide cutting edge coverage over only about one-half theinterior circumference of an artery and are most useful in removingplaque from the posterior side of an artery such as the femoral artery,where atheroma normally occurs only on the posterior side of the artery.The wire blades 34d without edges then help to maintain the properrelationship between the blades 34c, and keep the basket knife apparatuscentered within the arterial lumen.

In some instances a catheter atherotome may be required to be of a sizethat is too small to admit passage of the balloon-tipped catheter 30therethrough. It is still necessary to be able to retrieve pieces ofplaque which have been cut free from the interior wall of an artery byuse of the atherotome. In order to recover the matter excised from anarterial wall, a catheter atherotome 90, shown in FIGS. 11a and 11b,which is otherwise similar to the catheter atherotome 10, additionallyincludes a flexible tubular membrane in the form of a skirt 92 arrangedabout and attached to the blades 34. One end of the skirt is attached tothe distal fitting 66 by means of ferrules 91 and the other end isattached to the proximal fitting 76 by means of ferrules 93. The skirt92 is preferably adherently attached to the blades 34, at least alongthe middle portions 42, and slits 94 or equivalent openings are providedto expose the edges 44 and provide ingress for pieces of plaque to theinterior of the skirt 92. Pieces of plaque or the like cut free from theinterior wall of an artery are able to pass through the slits 94 to becollected upon retrieval of the catheter atherotome 90 from within anartery. The membrane used as the skirt 92 must be flexible and thin, yetstrong and elastic enough to accommodate the adjustment of the basketknife 32. A suitable material is a thin sheet latex. The skirt 92 may beattached to distal fitting 66 and the proximal fitting 76 after assemblyof the catheter atherotome 10 including the blades 34.

Referring now to FIGS. 12a, 12b, and 12c, showing a portion of an artery96 including an atheroma 98, the catheter atherotome 10 is illustratedschematically to show its use. As shown in FIG. 12a, the catheteratherotome 10 has been inserted into the artery from right to left.Thereafter, the inner member 14 has been withdrawn a distance into thedistal end 35 of the outer sheath 12, so that the blades 34 are bowed,to place the middle portion 42 of each blade at an increased radialdistance away from the inner member 14 and to cause the sharpened edges44 to come into proper position.

To excise a portion of the atheroma 98, the catheter atherotome ismanually pulled to the right as shown in FIG. 12b, and as indicated bythe arrow 100. As the inwardly projecting atheroma 98 is encountered bythe upper blade 34, and particularly by the edge 44, engagement of theedge 44 is in the atheroma plaque material causes the edge 44 to beeverted into a cutting position in which it digs into the plaquematerial and begins to cut a portion of the plaque material free, as maybe seen in FIG. 12c. Torsional forces developed in the strut portions 46and 48 control the angle of incidence of the edge 44, allowing themiddle portion 42 to be moved to such a cutting position when plaque isencountered. However, where there is no plaque material present as inthe lower portions of the artery shown in FIGS. 12a, 12b, and 12c, theedge 44 of the respective blade 34 is oriented so that it does not catchthe intima of the arterial wall and simply slides along the interiorwall of the artery without doing any cutting.

The surgeon using the catheter atherotome 10 can repeatedly move thebasket knife 32 back and forth in the area of an atheroma such as theatheroma 98, cutting away a thin layer of plaque with each pass in thedirection indicated by the arrow 100 in FIGS. 12b and 12c, until thelumen of the artery 96 has been opened sufficiently. After each cuttingstroke the entire catheter atherotome 10 will be rotated through anangle which can be determined by the position of the levers 16 and 18,so as to result in excision of plaque in an evenly distributed patternabout the interior of the artery. Thereafter, the inner member 14 may beallowed to resume its extended position beyond the distal end o theouter sheath 12, using the loop 20 (see FIG. 1) against the second stop25 if necessary, thus retracting the middle sections 42 of the blades 34closer to the inner member 14. The catheter atherotome 10 can then bewithdrawn from the artery, followed by withdrawal of the balloon-tippedcatheter 30, with the balloon 60 (see FIG. 1) inflated to retrieve thematerial which has been cut free from the arterial wall during theprocess.

The procedure is similar when using the catheter atherotome 90 (FIGS.11a and 11b), except that the material cut free from the arterial wallwould be retained within the membrane skirt 92 for retrieval along withthe atherotome 90 when it is withdrawn from the artery.

The catheter atherotome 10 may be introduced into an artery including astenosis by providing access to the artery and opening the arterial wallat a position more proximal to the heart than the location of thestenosis. Preferably, a guide wire is introduced into the artery andpast the stenosis. Thereafter, if required, a dilator may be introducedinto the artery, guided by the wire. The dilator may then be withdrawnand the catheter atherotome 10 according to the present invention may beinserted into the artery along the guide wire, which may then bewithdrawn and replaced by the balloon-tipped catheter 30. Afterinflation of the balloon 60 to prevent loss of pieces of material cutfree from the arterial will by the atherotome 10, the basket knife 32may be expanded to the required size by withdrawal of the inner member14 into the distal end 35 of the outer member 12 a required distance bysqueezing together the finger loops of the levers 16 and 18, so that theelongate loop 20 acts upon the stop 22 to withdraw the proximal end 21of the inner member 14 at the proximal end of the catheter atherotome10. Preferably, the scale 24 provided on the lever arm 16 may be used todetermine when the inner member 14 has been withdrawn sufficiently toprovide the required expansion of the basket knife 32.

Thereupon, the catheter atherotome may be withdrawn past the location ofthe atheroma, with the sharpened edges 44 of the blades 34 of the basketknife 32 paring away a portion of the plaque from the interior of theartery. The atherotome is then pushed into the artery until the blades34 are beyond the atheroma, and rotated to a desired position for asubsequent pull-back cutting stroke. After several strokes, for example,six to ten cutting strokes, sufficient enlargement of the lumen of theartery should have taken place, and the basket blade 32 can be relaxed,contracting the blades 34 into position alongside the inner member 14 asshown in FIG. 1, so that the atherotome can be withdrawn from theartery.

The terms and expressions which have been employed in the foregoingspecification are used therein as terms of description and not oflimitation, and there is no intention in the use of such terms andexpressions of excluding equivalents of the features shown and describedor portions thereof, it being recognized that the scope of the inventionis defined and limited only by the claims which follow.

What is claimed is:
 1. A method for performing partial atherectomy of anartery to enlarge the effective lumen thereof, comprising:making anopening through a wall of the artery at a location spaced apart from anatheroma and more proximal to a patient's heart than said atheroma;inserting a catheter atherotome having a basket knife including aplurality of blades in a closed orientation into said artery throughsaid opening; directing said catheter atherotome along the interior ofsaid artery to the vicinity of said atheroma; directing and moving saidcatheter atherotome further along the interior of said artery until saidbasket knife passes beyond said atheroma; opening said basket knife to afirst desired manually variable diametral cutting size orientation; andthereafter retracting said catheter atherotome along said artery adistance great enough to bring cutting blade edges of said basket knifeinto proximally disposed cutting engagement with said atheroma; andcutting away a portion of said atheroma only when said basket knife isnot being moved distally by only energy supplied for longitudinalretrogression of said catheter atherotome and said blades of said basketknife thereof.
 2. The method of claim 1 further including the steps ofredirecting said catheter distally across said atheroma with said basketknife in the first open orientation without cutting additional tissuefrom said atheroma, and thereafter opening said basket knife to a seconddesired manually variable diametral size orientation prior to said stepsof retracting and cutting to thereby cut away another portion ofatheroma.
 3. The method of claim 1 including the steps of inserting aballoon tipped catheter through a lumen defined by said catheteratherotome and inflating said balloon at a position beyond said atheromaprior to performing said step of retracting said catheter atherotome tocut away a portion of said atheroma, and including the further step ofwithdrawing said balloon-tipped catheter with said balloon inflatedafter completion of said step of retracting said catheter atherotome tocut away a portion of said atheroma, in order to retrieve material cutfrom said atheroma.
 4. The method of claim 1 wherein said step of makingan opening in said artery is performed percutaneously by inserting ahollow needle into said artery and thereafter inserting a guide wirethrough said hollow needle, thereafter removing said hollow needle anddirecting a dilator along said guide wire into said artery, andthereafter retracting said dilator and inserting said catheteratherotome along said guide wire into said artery.